Grid-bias battery



, 1931. w. E. BRINDLEY GRID BIAS BATTERY April 21 Filed Sept. 8, 1923 INVENTOR William E Brindley.

' WT SE:

Patented Apr. 21, 1931 UNITED STATES PATENT OFFHQE W ILLIAM E. BRINDLEY, OF WILKTNSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, AGORPORATION 0F PENNSYL- VANIA GRID-BIAS BATTERY Application filed September 8, 1923. Serial No. 661,578.

My invention relates to radio signaling by thermionic discharge devices.

Broadly speaking, the object of my invention is to provide a more convenient supply of grid bias potential for the grids of three electrode thermionic devices. a

More specifically, the object of my invention is to provide a grid bias potential derived. from the plate battery which is associated with all such thermionic devices.

It has been found desirable to apply the grid bias potential to the grids oftriodes employed for a multiplicity of purposes. In the prior art, this has been done by the pro vision of a separate battery connected in the grid circuit and serving no other purpose. The presence of this grid battery is objectionable, inasmuch as it is additional apparatus, requires additional maintenance.

My invention produces a means of supplying the desired potential upon the grid from a source already present for other purposes.

Other objects and structural details of my invention will be apparent from the following description and claims when read in connection with the accompanying drawings wherein:

Figure 1 is a diagrammatic view of a detector and amplifier constructed in accordance with my invention and Fig. 2 is a diagrammatic view of a detector and a push pull amplifier constructed in accordance with my invention.

In Fig. 1, a single battery 1, called in the prior art a B battery, furnishes grid bias potential for both a detector and an amplifier triode as well as plate current for the detector and amplifier triodes. In Fig. 1 is shown a radio receptor circuit comprising an aerial 2, tuning condenser 3, inductance 4 and ground 5. To inductance & is coupled a secondary inductance 6 connected between the grid and cathode of detector triode 7 in the usual manner, and a tickler coil 8 is also placed in inductive relation to coils t and 6, one terminal being connected to the plate of triode 7 and the other terminal to the primary of amplifying transformer 9 which is shunted with a radio frequency by pass condenser 11. The other terminal of the primary of transformer 9 is in turn connected to a portion of high voltage battery 1, this portion being chosen of such size as to he most suitable for the characteristics of the particular detector tube employed. The neg ative terminal of battery 1 is connected to coil 6 and through coil 6 to the grid of triode 7. The filament of triode 7 is connected to a tap on battery 1, thereby making the grid of triode 7 negative with respect to the filament. The amount of negative potential is chosen of a magnitude suitable to cause triode 7 to function as a detector.

The presence of condenser 11 allows the regenerative functions to occur in the manner well known in the prior art and forces the audio frequency currents to pass through the primary winding of amplifying transformer 9. One terminal of the secondary winding of transformer 9 is connected to the grid of an amplifier triode 12 and the other terminal of thesecondary winding is connected to the negative terminal of battery 1. The plate of the through the signal receiver 13, which will usually be a telephone, to the positive terminal of battery 1.

The filament of amplifier triode 12 is connected to a tap on battery 1 which may or may not be the same as that to which the filament of triode 7 is connected. The tap to which the filament of triode 12 is connected is chosen to give such a grid bias with respect to the filament in triode 12 as is found to be most suitable for accurate reproduction and amplification without distortion of signals by the triode12.

Figure 2 shows a slightly different. embodiment of my invention. As before, the battery'l is provided as a source of plate current for detector triode 7. An aerial 2, condenser 3, tuning inductance 1 and ground 5 are provided as in the preceding embodiment. A tickler coil 8 connected between the primary of amplifying transformer 19 and the plate of triode 7 is provided. The other terminal of the primary of transformer 19 is connected to the positive terminal of battery 1. The primary and battery are shunted by condenser 11 as shown, thereby amplifier triode 12 is connected loo making regenerative detection possible by triode 7.

The filament of triode 7 is connected to the negative terminal of battery 1 in the manner shown, which is common to the prior art. The grid of triode 7 is connected to grid leal; and grid condenser '14 according to the prior art. The connections so tar described are substantially those of the prior art of the deteotion oi radio signals by triode valves. Any convenient triode detector assembly may be substituted for this assembly, provided that it is adaptable to cooperate with the special amplifying transformer 19.

A. push pull amplifier assembly 20 is included in this embodiment of my invention. This amplifier comprises triodes 21 and 22, transformers 19 and 23, connections as shown on the drawing a source of B battery potential as indicated by the letter B on the drawing, but not shown, and a source or" A battery as also indicated, but not shown.

The push pull amplifier 2O ordinarily requires a grid bias potential on both triodes 21 and 22 which depends to a considerable extent upon the B battery potential ap plied. In the construction of the prior art, a separate battery is required for the purpose of supplying this necessary grid bias. My invention however, employs a portion of the plate battery of the detector triode to furnish the potential. This is done by connecting the grids of the two triodes 21 and 22 through their respective secondaries of transformer 19 to the negative terminal of battery 1 and connecting the filament to the tap on battery 1 at such point as to give the proper potential.

In operation, it will be obvious that the construction of Fig. 1 will place the negative potential with respect to the filament upon the grid of detector 7, which is determined by the value of the potential developed by battery 1 in the portion included between the negative terminal and the tap to which is connected the filament of detector triode 7, and that a negative potential with respect to the filament will be placed upon the grid of triode 12, determined by the potential of that portion of battery 1, included between its negative terminal and the tap to which is connected the filament of the amplifier triode.

It is obvious that, by means of the construction described I produce upon the grids of the triodes of my device a suitable grid bias potential without the necessity of providing additional individual grid bias or C batteries.

While I have shown only two embodiments of my invention of the accompanying drawings, it is capable of various changes and modifications without departing from the spirit thereof and it is desired therefore that only such limitations shall be imposed thereon as are indicated in the prior art or in the appended claims.

I claim as my invention:

1. in combination, a plurality of thermionic devices each having a cathode, a plate and a grid, a single source of potential for the plates of said tubes, connections between said grids and the negative pole of said source, and variable connections from said cathodes to sa'd source, whereby the grid of one of said devices may be biased to a potential more negative than its cathode by a portion of said source that supplies plate potential for another of said devices.

2. In combination, a plurality of thermionic devices each having a cathode, a plate and a grid, a high-potential source, a connection from one of said cathodes to an intermediate point on said source, a connection from another of said cathodes to another intermediate point on said source, connections whereby said source supplies negative bias to said grids and additional connections whereby said source supplies positive potentials to said plates.

In testimony whereof, I have hereunto subscribed my name this 28rd day of August, 1923.

WILLIAM E. BRINDLEY. 

